Process of producing uranium tetrachloride



May 4, 1954 J. M. CARTER PROCESS OF PRODUCING URANIUM TETRACHLORIDE Filed June 10, 1943 mwkmcu mxmmt NW A Q I h .MWUWU amt 29b QB mm. mm mm X 28 FE iuu -so -68 6U --02 mmwm cotommmi Q I T U I INVENTOR. James M. Carfer BY g i E:

ATTORNEY.

Patented May 4, 1954 PROCESS OF PRODUCING URANIUM TETRACHLORIDE James M. Carter, Berkeley, Calif., assignor to the United States of America as represented by the United States Atomic Energy Commission Application June 10, 1943, Serial No. 490,293

9 Claims.

The present invention relates to processes of producing uranium tetrachloride, and more particularly, to such processes using carbon tetrachloride and the various oxides of uranium.

It is an object of the invention to provide an improved process of producing uranium tetrachloride of high chemical purity in crystalline form, wherein a majority of the product has a relatively large crystalline grain size.

Another object of the invention is to provide an improved carbon tetrachloride and uranium oxide process of producing uranium tetrachloride in which the reaction temperature is maintained within an optimum range, whereby the product is of the desired crystalline structure and side reactions productive of other uranium chlorides and other objectionable compounds are minimized.

Another object of the invention is to provide an improved process of producing uranium tetrachloride which employs reactions of a mixture of carbon tetrachloride vapor and phosgene with an oxide of uranium.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification, taken in connection with the accompanying drawing, in which the single figure is a schematic illustration of apparatus suitable for carrying out the processes of the present invention.

In accordance with the present invention, a suitable charge of uranium oxide (U02, U03 or U308) is placed in a reaction chamber surrounded by a heater and heated to a reaction temperature, the interior of the reaction chamber near the charge being maintained at a temperature within the range 425 to 475 0., and as near 459 C. as practicable, the pressure meanwhile being substantially atmospheric. Liquid C014 is conducted through a conduit arranged adjacent the reaction chamber and surrounded by the heater, whereby C014 is converted into the vapor phase and heated to a temperature of the order of 500 C. The hot C014 vapor is then conducted into the interior of the reaction chamber into direct contact with the charge of uranium oxide, whereby the hot 0014 vapor reacts with the hot charge of uranium oxide to produce uranium tetrachloride and certain reaction gases, including 00, 002, 00012, and C12. The reaction gases and the unspent C014 vapor are conducted from the reaction chamber through a suitable condenser, whereby substantially all the unspent C014 vapor is condensed and the reaction gases are exhausted. Preferably, the condensed C014 is again conducted to the conduit for reconversion into the vapor phase, whereby the unreacted C014 is recycled repeatedly.

During the process, additional C014 is supplied as it is consumed in the reaction with the charge of uranium oxide, and the process is continued until all of the charge of uranium oxide has been converted into U014. At this time, when the reaction of the charge of uranium oxide is complete, the evolution of reaction gases ceases, thereby providing a ready indication of the completion of the process. Further, it is noted that the 00012, produced as a reaction gas is appreciably soluble in 0014, whereby the charge of uranium oxide is reacted with a mixture of 0014 vapor and 00012 after the process is initiated. Thus, the 00012 also reacts with the charge of uranium oxide to produce U014. The fact that 00012 reacts with the charge of uranium oxide to produce U014 is manifest by the consumption of less than two moles of 0014 to produce one mole of U014, as more clearly indicated hereinafter.

Ordinarily, the process requires approximately four and one-half hours to complete the reaction at the reaction temperature mentioned, whereby substantially all of the charge of uranium oxide is converted into U014 and appears in crystalline form of dark green color, a majority of the product having a crystalline grain size between 10 and mesh. It is noted that during the course of a run it is well to tap or shake the reaction chamber lightly at suitable time intervals, in order to prevent caking of the product and to cause the unreacted portion of the charge to be presented to the surface to be contacted and reacted.

While the process may be carried out at a reaction temperature below the lower end of the preferred range, at a temperature of 400 0., for example, in order to produce U014, this product so produced is in the form of a rather fine greenish colored powder and has a tendency to lump very badly. In addition, the reaction proceeds much more slowly. Similarly, while the process may be carried out at a reaction temperature above the upper end of the preferred range, at a temperature of 500 0., for example, in order to produce U014 of the desired crystalline structure, the side reactions productive of other uraniuin chlorides, such as U015, and various other objectionable compounds such as C2C16, from breakdown of 0014 at this temperature are exceedingly objectionable in that the U015 escapes from the apparatus and clogs feed and exit lines; the product may be contaminated with U015,

CzCls, and other substances, and large amounts of 0014 are wasted. On the other hand, when the process is carried out at a reaction temperature within the preferred range, substantially complete conversion of the charge is effected, and the product is of a very high chemical purity and of the desired crystalline form, a majority of the product having a crystalline grain size between and 60 mesh. Also in this event, a minimum amount of 0014 is utilized in the reaction and side reactions productive of other uranium chlorides and other objectionable compounds are minimized. This product so produced, having the desired crystalline structure, is particularly wellsuited for use in vacuum apparatus in which it may be vaporized or sublimed in carrying out other processes or methods, in that the product being of relatively large crystalline structure may be readily out-gassed, and has little tendency to be transported as dust in the vacuum apparatus.

After the U014 has been produced in accordance with the present process, it i poured from the reaction chamber into a dried container and maintained under a storage atmosphere of CO2. Subsequently, the product is transferred to a dry cabinet containing 002 and screened, in order to separate out undesirable ends and a minor portion of the product in fine powdered form. More particularly, the useable product is that which will pass a IO-mesh screen and will not pass a GO-mesh screen, a large fraction of the useable product having a crystal grain size between 10 and mesh. The useable product is then bottled in an atmosphere of 002 or in a vacuum, and sealed for future use in vacuum apparatus.

E :ramples When the process is carried out employing U02, 600 grams of U02 are converted by the required amount of 0014 to obtain a complete reaction into 844 grams of U014; and it is believed that the following specific reactions take place:

Both 00012 and 002 have been found in the exit gases.

Similarly, when the process is carried out employing U03, 600 grams of U03 are converted by the required amount of 0014 to obtain a complete reaction into 800 grams of U014, and it is believed that the following specific reactions take place U03 3CC14- UC14+3CO C12 C12 U03 +3COC12- UC14+ 3002 C12 00012, 002, and 012 have been found in the exit gases.

4 In carrying out the present process, utilizing a charge of U02, a typical run is productive of U014 having a crystalline structure of the desired grain size as indicated below:

l Based on 01 analysis.

Referring now more particularly to the single figure of the drawing, there is illustrated suitable apparatus for carrying'out the present process, which comprises an inclined support It carrying a hollow tubular heater H of any desired type. Arranged within the opening in the heater l I are a tubular Pyrex reaction chamber l2 and a glass conduit l3, the conduit is being disposed adjacent the reaction chamber l2 and in slightly closer proximity to the wall of the heater 5!. The reaction chamber I2 contains a suitable charge Id of uranium oxide and the opposite ends thereof areclosed by suitable removable stoppers I5 and 16. Also, the apparatus comprises a reservoir I! of the constant head-feed type, and containing 0014, a connected feed-drop counter 18, and a connected substantially U-shaped liquid seal 19. One end of the liquid seal :5 is connected by a suitable ground glass joint 20 to one end of the conduit [3; and a suitable surge damper stop-cock 2| is interposed between the other end of the liquid seal 19 and the feed-drop counter I8. Also, the feed-drop counter 58 communicates with the atmosphere through a tube 22 containing a packing of a suitable drying agent such, for example, as 0a0l2. The other end of the conduit I3 is connected by a ground glass joint 23 to a tube 24 extending through the stopper l6 into the interior of the reaction chamber l2.

Further, the apparatus comprises a dust and U015 trap 25 connected by ground glass joints 25 and 21 to two tubes 28 and 29, respectively, the tube 28 being connected by a ground glass joint 3b to an upstanding tube 3|, and the tube 29 extending through the stopper [5 into the interior of the reaction chamber [2. The upper end of the upstandin tube 3| is surrounded by a suitable condenser 32, through which a suitable cooling liquid such, for example, as water, is conducted; and the lower end of the upstanding tube 3'l terminates in a return drop counter 33. The lower end of the return drop counter 33 is connected by way of a ground glass joint 34 and a stop-cock 35 to the reservoir ll. Also, the reservoir I1 and the lower end of the return drop counter 33 are connected by way of a surge damper stop-cock 36 to the feed-drop counter 58.

Considering now the operation of the apparatus, liquid C014 is conducted from the feed-drop counter l8 by way of the surge damper stop-cock 2| into the liquid seal [9, the surge damper stopcock 2| being adjusted to prevent surge of liquid 0014 back into the feed-drop counter l8. From the liquid seal 19 the liquid C014 flows downwardly into the inclined conduit it, where it is converted into the vapor phase and passed via the tube 24 into the interior of the reaction chamber 12 into contact with the hot charge I4. A portion of the charge 14 of uranium oxide is converted into U014, and certain reaction gases are produced, as previously noted. The unspent 0014 vapor and the reaction gases are then swept from the reaction chamber [2 through the tube 29 into the dust trap 25, and flow therefrom through the tube 28 into the upstanding tube 35. All of the reaction gases insoluble in 0014 pass through the upper end of the upstanding tube 3! and are exhausted, while C014 vapor entering the upper end of the upstanding tube 3! is condensed by the condenser 32 and flows downwardly into the return drop counter 33. The condensed C014 flows from the return drop counter 33 again into the feed drop counter 58, and is repeatedly recirculated. The 0014 which is reacted is made up for by additional 0014 introduced into the circulating system from the reservoir ii", the additional C014 mention-ed flowing via the stopcook 35 and the surge damper stop-cock 36 with the condensed 0014 from the return drop counter 33 into the feed drop counter It. The stop-cock 35 is adjusted so that the supply of C014 from the reservoir I? and the return drop counter 33 into the liquid seal I9 is appropriate to supply the necessary 0014 into the conduit 53 and to prevent flooding of liquid 0014 through the conduit it into the reaction chamber I2. As previously noted, a portion of the 00012 produced as a reaction gas in the reaction chamber l 2 is dissolved in the C014 and is circulated in the system with the C014, whereby the charge I i of uranium oxide is reacted by the mixture of 0014 vapor and 00012.

It will be understood that the time of four and one-half hours mentioned as being suitable for carrying out a complete reaction refers only to the specific examples given utilizing a charge of a fixed number of grains of uranium oxide in a reaction chamber of specified size and shape. By using a smaller amount of uranium oxide and/or increasing the proportionate surface of the charge exposed to the action of the vapors, the time required for a complete reaction of the charge may be considerably reduced. For example, charges of 5 to 26 grams of U02 have been substantially completely converted (98+%) to U014 in to 20 minutes.

It is pointed out that the oxide of uranium preferred as a charge in this reaction is U02, in that it has several advantages over the other oxides mentioned. In the first place, a charge or" U02 reacts much more rapidly than a charge of either U308 or U03, a charge of U03 reacting most slowly of the three uranium oxides men tioned. Also, in U02 the uranium is already in the same valence state as it is in the product U014; no chlorine is produced in the reaction; and there is accordingly less tendency to form U015 and other objectionable compounds. Finally, as a corollary of the fact that a charge of U02 is most rapidly converted, this more rapid reaction is advantageous in avoiding the formation of U015 and other objectionable compounds, as the reaction temperature can be kept toward the lower end of the preferred range.

While there has been described what is at present considered to be the preferred embodiment of the process, it will be understood that various modifications may be made therein and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed'is:

1. The process comprising reacting carbon tetrachloride vapor with an oxide of uranium at a reaction temperature within the range 425 to 475 0., and maintaining the temperature within said range until the oxide is substantially completely converted to crystalline uranium tetrachloride, the major portion cf the product having a crystal grain size between 10 and 63 mesh.

2. The process comprising contacting carbon tetrachloride vapor with an oxide of uranium at a reaction temperature within the range 425 to 475 0., whereby uranium tetrachloride and reaction gases including phosgene are produced, condensing the unreacted carbon tetrachloride vapor, whereby carbon tetrachloride is separated thereby dissolving some of the phosgene from the remainder of the reaction gases, and reconverting the liquid carbon tetrachloride and dissolved phosgene into vapor to be contacted again with the unreacted oxide of uranium, whereby the unreacted carbon tetrachloride and some of the phosgene are recycled repeatedly and maintaining the temperature within said range until the oxide is substantially completely converted to crystalline uranium tetrachloride, the major portion of the product having a crystalline size between 10 and 60 mesh.

3. The process comprising reacting C014 vapor with U02 at a reaction temperature within the range 425 to 475 0., and maintaining the temperature within said range until the oxide is substantially completely converted to crystalline U014, the major portion of the product having a crystal grain size between 10 and 60 mesh.

4. The process comprising reacting C014 vapor with U03 at a reaction temperature within the range 425 to 475 0., and maintaining the temperature within said range until the oxide is substantially completely converted to crystalline U014, the major portion of the product having a crystal grain size between 10 and 60 mesh.

5. The process comprising reacting 0014 vapor with U308 at a reaction temperature within the range 425 to 475 0., and maintaining the term perature within said range until the oxide is substantially completely converted to crystalline U014, the major portion of the product having a crystal grain size between 10 and 60 mesh.

6. The process comprising reacting a mixture of carbon tetrachloride vapor and phosgene with an oxide of uranium at a reaction temperature within the range 425 to 475 0., and maintain-- ing the temperature within said range until the oxide is substantially completely converted to crystalline uranium tetrachloride, the major portion of the product having a crystal grain size between 10 and 60 mesh.

7. The process comprising reacting a mixture of 0014 vapor and 00012 with U02 at a reaction temperature within the range 425 to 475 0., and maintaining the temperature Within said range until the oxide is substantially completely converted to crystalline U014, the major portion of the product having a crystal grain size between 10 and 60 mesh.

8. The process comprising reacting carbon tetrachloride vapor with an oxide of uranium selected from the group consisting of U02, U03 and U308 at a reaction temperature within the range 425 to 475 0., and maintaining the temperature within said range until the oxide is substantially completely converted to crystalline uranium tetrachloride, a major portion of the product having a crystal grain size between 10 References Cited in the file of this patent and so mesh- UNITED STATES PATENTS 9. The process comprising reactmg carbon tetrachloride va'por with an oxide of uranium at Number Name Date a reaction temperature of approximately 450 C., 5 2,150,366 Ehrhart 1939 and maintaining said temperature until the oxide 2178'685 Gage 1939 is substantially completely converted to crystal- OTHER REFERENCES line uranium tetrachloride, the major portion of M61101. Comprehensive Treatise on Inorganic the product having a crystal grain size between and Theorefical Chemistry, vol XII pages 30 and 60 mesh- 10 and 81. (Copy in Division 59.)

Chem. Abstracts 5 1036. (Copy in Division 6.) 

1. THE PROCESS COMPRISING REACTING CARBON TETRACHLORIDE VAPOR WITH AN OXIDE OF URANIUM AT A REACTION TEMPERATURE WITHIN THE RANGE 425* TO 475* C., AND MAINTAINING THE TEMPERATURE WITHIN SAID RANGE UNTIL THE OXIDE IS SUBSTANTIALLY COMPLETELY CONVERTED TO CRYSTALLINE URANIUM TETRACHLORIDE, THE MAJOR PORTION OF THE PRODUCT HAVING A CRYSTAL GRAIN SIZE BETWEEN 10 AND 60 MESH. 